Lots of good tips so far, and good stories... The easiest way to do it all VFR is to constantly check your position and set boundaries for your flight.
I start my typical ground lesson on navigation like this:
"If you navigate effectively, you won't get lost. If you navigate proficiently, you'll know where you are at all times."
So in essence, draw that line on your chart and do your best to look outside the aircraft and make sure you are as perfectly on that line as possible. Even small objects such as quarries and football stadiums can help precisely orient you.
As for boundaries, pretend you are giving yourself directions. For instance, "I'm going keep XXX interstate on my left, XX river on the right, and If I get to XXX lake I've gone too far. "
Good luck on your next X/C. I'm sure you'll do fine!